1. Field of the Invention
The present invention is related to a method of manufacturing toner and toner. Manufactured by the method
2. Description of the Background Art
Image forming apparatuses such as photocopiers and printers that produce quality images at a high speed continue to be in great demand. In keeping with this trend, improved thermal and/or mechanical stress resistance is required of toner used in such apparatuses, whether the toner is one-component development agents or two-component development agents. In particular, the physical force of attachment between toner particles and either carrier particles or a development agent bearing member during the electrophotographic development process contributes to good development of images. However, additives present on mother toner particles are embedded therein by the thermal and/or mechanical stress applied to the particles at a development unit during development, resulting in an increase of the physical force of attachment, which in turn causes problems such as reduction of the developability and/or transferability, non-uniform transfer, degradation of fluidity, non-uniform charge, and vulnerability to environmental changes.
To solve these problems, there is a method that provides particles having a larger diameter than that of the additives are used in combination. However, such particles are not able to reduce embedding of the additives unless such particles are fixed on the surface of mother toner particles in at least a certain amount.
Since particles having a larger diameter than that of the additives have a small specific surface area, the added amount of the particles are required to increase in some degree and also the particles are required to be fixed on the surface of mother toner particles. In particular, in the case of a polymerized toner having a core-shell structure for low temperature fixing with a surface having no releasing agent present on mother toner particles, it is difficult to fix such large-diameter particles on the mother toner particles.
At the same time, additives can be fixed on the surface of mother toner particles by various known methods. For example, Japanese patent application publication No. S63-85756 (JP-S63-85756-A) describes a method of attaching inorganic fine powder to the surface of core material by mechanical and thermal energy using mainly impact power. JP-S63-139366-A describes a method of removing fine powder of silicic acid not attached to mother toner particles. JP-H10-10781-A describes a method of instantaneously heating a mixture of thermoplastic particles and additives without contact in the atmosphere ranging from the softening point of the thermoplastic resin to 300° C. higher than that JP-H10-95855-A describes a method of using a spherical mixer having a lower rotation wing rotating along the basal plane of the spherical vessel and an upper rotation wing provided at the center thereof rotating at a peripheral speed of 40 m/s or higher.
Further, JP-2005-270955-A describes a method of using a processor that is provided with a rotary shaft with two or more agitation members installed in a circumference section, and a casing having the inner circumference section located apart from the agitation members at a minute interval, such that, when the treatment apparatus is viewed from the direction orthogonal to the axial direction of the rotary shaft, the end position of each of the agitation members in the direction parallel to the axial direction of the rotary shaft is located inside of the other adjacent agitation members rather than at the end position of the other agitation members.
JP-2004-77593-A describes a method of manufacturing an electrophotographic toner in which toner matrix particles consisting essentially of a binder resin, a colorant, and a releasing agent, and an electrostatic charge controlling agent, are stirred together by rotating a rotator having stirring blades in a fluidized stirring-type mixing apparatus to fix the electrostatic charge controlling agent on the surfaces of the toner matrix particles. The rotator is rotated at 65 to 120 m/s peripheral speed within a temperature range of Tg-10>T>Tg-35 (where T is the temperature (° C.) of the internal atmosphere of the apparatus during stirring and Tg is the glass transition temperature (° C.) of the resin powder).
JP-2009-69640-A describes a method of manufacturing an electrophotographic toner to fix a charge control agent to the surface of the mother toner particle by a flowing and stirring type mixer in which a mixture of 100 parts by weight of the mother toner particle, 0.3 to 1.0 part by weight of a charge control agent having a primary particle diameter of from 5 to 1,000 nm, and an inorganic particulate having a specific surface area diameter of from 5 to 300 nm are stirred in a range satisfying the relation Tg-50<T<Tg-15 (where T represents a temperature (° C.) of the atmosphere in the flowing and stirring type mixer during stirring and Tg represents the glass transition temperature (° C.) of the mother toner particle). The flowing and stirring type mixer has a rotation axis, multiple stirring members, a casing having a circular wall face with a constant distance from the rotation axis, and a cooling jacket. In addition, the multiple stirring members are provided to the rotation axis in such a manner that the stirring members rotate in three or more different circular paths having diameters of from 90 to 1,000 mm at a peripheral speed of from 10 to 150 m/s. Furthermore, the clearance C (mm) between at least one of the multiple stirring members and the circular wall face and the diameter D (mm) of the maximum circular path among the circular paths satisfies the relation 2.5≦D1/2/C<9.0. The mother toner particle contains a binder resin, a coloring agent, and a releasing agent, and has a weight average particle diameter D4 of from 3 to 9 μm.
Finally, JP-H09-230622-A describes a method of manufacturing electrophotographic toner formed by admixing particulates with colored particles consisting of at least a resin and a colorant, wherein the toner has a mean particle size by volume of from 50 to 1,000 nm and organic particulates having frictional charging characteristics of the same polarity as the colored particles with regard to a frictional charging member are fixed to the surfaces of the colored particles, followed by admixing inorganic particulates having a mean particle size by volume of from 5 to 50 nm.
Although these methods are successful to some extent, they are unsatisfactory with regard to the amount of the large-diameter particles that are fixed on the surface of the mother toner particles. As a result, these additives gradually bury into the mother toner particles during image formation over a long period of time.